make lv_examples compatible for use with Arduino

[ataweg]

for using lv_examples as library in the Arduino ecosystem please replace
#include <lv_examples/lv_demo.h>
with
#include "../lv_demo.h"
I thick this should also work in other environments.

[Gabor Kiss-Vamosi]

Thanks, fixed.

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Gabor Kiss-Vamosi]

It should be fixed so I close it.